The present invention relates to the optical effect art. It finds particular application to an article having variable optical effects based on its viewing angle and a method and system for making such article. It will be appreciated that the present invention can be applied to a variety of articles such as wall paper, signs, logos, designs, vinyl covers or any other article that may contain an optical effect.
One type of optical effect can be produced on an article by having a relief pattern formed on its surface. The relief may be in the form of a geometrical figure, a number, a letter, an ornament, a guilloche, etc., and may be formed for example by stringing together a large number of relatively small optical-diffraction elements. Such relief patterns may be achieved by virtue of the fact that diffraction structures can be produced by interferometric superimposition of coherent light beams with different angles of incidence, which are converted by photolithographic means into the surface microprofile. Fixed prefabricated optical masks can be used for geometrically defining the areas to be exposed to light. If the relief pattern to be produced and its microscopic structure exceed a given degree of graphic and structural complexity, the mask procedure is found to be prohibitively expensive. In addition, optical-diffraction structural elements with an asymmetrical profile, for example sawtooth configurations, cannot be produced by the above-mentioned interferometric method.
Another type of optical effect can be produced using structures exhibiting an optical diffraction effect such as phase diffraction gratings, phase holograms and the like. The structures can be formed on an article by stamping or embossing a thermoplastic substrate by means of an embossing die, using pressure and heat. The synthesis of a surface pattern having an optical diffraction effect could also be effected by numerous phase diffraction elements being strung together by repeated embossing in a thermoplastic substrate. This method, however, achieves unsatisfactory results because troublesome beads are produced at the edges of the embossing region between the heated pressure region and the unheated non-pressure area outside the embossing region. Beads are also produced between different image objects and adjacent areas on the surface. In addition, the various embossing regions cannot be fitted together without a joint or seam therebetween, as the high thermal mass of metal embossing dies means that, at the edge of a new embossing region, the edge region of the adjacent old embossing region is necessarily erased.
In other prior embossing techniques, an original stipple pattern is created from grit or gravel and pieced into a PVC sleeve. This is then electroplated into a copper sleeve and mounted on a cylinder. A vinyl sheet is then embossed with the stipple pattern by pressing the cylinder over the sheet. In order to obtain a long embossed sheet, two or more cylinders are needed. However, each cylinder is made independent of the others and, thus, will have a different pattern due to different electroplating conditions and other variables involved in making the cylinder. Furthermore, a seam is typically visible between regions.
The present invention provides a new and unique method and system for forming an article having an optical effect which cures the above problems and others.
In accordance with the present invention, a method of forming an article having an optical effect is provided. A digital image of a texture is provided. The texture in a selected portion of the digital image is then modified to be different that other areas of the texture. The digital image is then reproduced into an article where the selected portion has an optical effect different than other portions of the article.
In accordance with a more limited aspect of the present invention, modifying includes angularly offsetting a direction of the texture in the selected portion.
In accordance with another aspect of the present invention, an article having an optical effect is provided. The article includes an engraved surface which has a textured grain. A shape is defined in the engraved surface where the textured grain within the shape is different that the textured grain on other portions of the engraved surface. The shape is visually distinguishable in the engraved surface at selected viewing angles.
In accordance with a more limited aspect of the present invention, the textured grain within the shape is in an opposite direction than the textured grain outside the shape. When the article is viewed from a first angle, the textured grain within the shape appears shadowed while the textured grain outside the shape appears light, thus, the shape is visually distinguishable.
In accordance with another aspect of the present invention, a system for forming a latent image on a material is provided. A scanner digitizes a stipple pattern to obtain a digital stipple pattern. An image processor defines an area in the digital stipple pattern by offsetting the stipple pattern within the area. A laser engraves the digital stipple pattern on a material where the area exhibits a different optical effect than other portions of the material.
One advantage of the present invention is that optical effects can be produced on an article without having beads or seams between different regions of an engraved texture. Furthermore, a latent image is produced on a article without using reflective materials or other light diffusing elements.
Another advantage of the present invention is that an optical effect is produced in a texture by changing the shadow effect within a selected region of the texture. A laser then precisely engraves the texture thus eliminating mechanical embossing techniques.
Yet another advantage of the present invention is that articles such as wallpaper or signs can be engraved with instructional messages or directions which are visible at certain viewing angles and invisible at other angles. In this manner, the decorative aspect of a wallpaper is not sacrificed.
Still further advantages of the present invention will become apparent to those of ordinary skill in the art upon reading and understanding the following detailed description of the preferred embodiments.